Imagine the fireworks that would go off if Mexican prosecutors charged a U.S. Border Patrol agent with the shooting death of Sergio Hernandez Guereca, a Mexican teen killed along the Rio Grande river basin between Ciudad Juarez and El Paso?

During his recent visit to Houston, Mexican President Felipe Calderon apparently left the door open to such a scenario – among many options- when he said his country was pushing ahead with an investigation of the incident, which the U.S. Department of Justice closed last week saying there was not enough evidence to support charging the agent.

“We really have to protect our countrymen here in the United States and protest, and follow-up, including judicially the deaths of many of our countrymen at the hands of the Border Patrol,” he said during a question and answer session with the Mexican community.

Then he went to the latest case:

“We have a case presented against judicial authorities, against the U.S. immigration authorities,” he said. “We have a process aimed at clarifying this killing,” he said. “Moreover, a process that our own attorney general put forth, and is ongoing precisely to investigate this (and other cases.”)

It is unclear if Calderon was speaking about criminal charges or supporting civil lawsuits, or both.

He did say that Mexico has seen too many of its citizens killed in the United States and that it has their backs by looking into the incidents. That includes this one, which occurred in the dry bed of the Rio Grande, as it cuts between Juarez and El Paso.

Each country can lay claim to a half of the waterway, with the borderline – and jurisdiction of each country’s laws – going right down the middle.

Of course, even if Mexico were to charge the agent, there would a far less than zero of a chance that agent would be extradited to Mexico to face justice there. And so, any such actions would just be part of a show that would play out well at home, but dump cold water on relations between the two countries, from the politician level to the level of law-enforcement agents on the ground.

Mexico President Felipe Calderon

Calderon’s comments came just days before the Department of Justice announced Friday that it was closing an investigation into the shooting on the grounds that there was insufficient evidence to further pursue criminal charges.

U.S. prosecutors concluded they could not prove beyond a reasonable doubt that the agent broke the law on June 7, 2010, when he shot Hernandez Guereca.

“The team of experienced prosecutors examined the shooting as a possible violation of U.S. criminal civil rights laws and as a possible violation of federal homicide statutes. With regard to the federal homicide statutes, the team of prosecutors and agents concluded that there is insufficient evidence to pursue prosecution of the (U.S. Customs and Border Protection) agent for a federal homicide offense. This review took into account evidence indicating that the agent’s actions constituted a reasonable use of force or would constitute an act of self-defense in response to the threat created by a group of smugglers hurling rocks at the agent and his detainee.”

It notes that 25 law enforcement officers and civilians were interviewed during the investigation and that in addition to collecting and analyzing evidence at the scene of the shooting, they reviewed law enforcement radio traffic, 911 recording, surveillance video and other material such as the agent’s disciplinary record.